The invention relates to marine engine cooling systems, and more particularly to a supplemental cooling system and water pickup therefor.
A marine engine has a main cooling system including gearcase water inlets supplying cooling water to the engine. A shaft-driven pump in the gearcase pumps cooling water from the inlets upwardly to the engine. At high boat speed, the pump may not be able to deliver enough cooling water to the engine and/or the gearcase water inlets may be above or partially above the waterline or otherwise aerated when the boat is on plane.
The present invention provides a supplemental cooling system supplying supplemental cooling water to the main cooling system to provide additional cooling for the engine, particularly at high boat speed.
In one aspect of the invention, a low drag water pickup is provided, minimizing boat drag otherwise caused by an additional water pickup. This in turn minimizes the reduction in top end boat speed.
In another aspect of the invention, a flow control valve is provided which includes a check valve between the main cooling system and the supplemental water pickup and supplying supplemental cooling water therethrough when main cooling system water pressure on the downstream side of the check valve is less than supplemental cooling system water pressure on the upstream side of the check valve, and blocking supplemental water flow therethrough from the supplemental water pickup to the main cooling system when main cooling system water pressure on the downstream side of the check valve is greater than supplemental cooling system water pressure on the upstream side of the check valve.
In another aspect of the invention, a continuous flow control valve is provided and enables continuous water flow therethrough to either the main cooling system or to a bypass relief outlet at high boat speed, to minimize deadhead pressure and boat drag. The flow control valve includes a relief valve between the check valve and the supplemental water pickup and discharges excess supplemental cooling water from the water pickup when the check valve is blocking water flow therethrough and supplemental cooling system water pressure is above a given relief threshold.